MONTE-CARLO STUDIES OF THE EXCLUDED VOLUME PROBLEM FOR OFF-LATTICE POLYMER-CHAINS

The expansion factor alpha R2 of model polymer chains 500 links long subject to excluded volume restraints has been studied using Monte Carlo techniques. The chains were synthesised in the spatial continuum, and the Wall and Erpenbeck enrichment technique was used to overcome chain attrition. The main conclusions to be drawn from the work are as follows: (i) It is possible that one of the four closed-form expressions for alpha R2 adequately represents the expansion of the chains up to nu =0.6, where nu is the excluded volume ratio. A condition is N>or approximately=100 for nu =0.2, increasing to N>or approximately=500 for nu =0.6, where N is the number of links in the chain. (ii) The excluded volume should be taken as eight times the volume of the sphere representing the polymer repeat unit for chains with freely varying bond angles, and twice the sphere volume for chains with tetrahedral bond angles. (iii) The data at small nu are in agreement with the perturbation theory expansion for alpha R 2 up to at least z approximately 0.03.